// 起始时间
// 1980年1月1日星期二
// 一年有365天 366天
// 需要算出今年是365天还是366天

var year = 2019;
var mounth = 5;

document.querySelector("#nian").innerHTML = year;
document.querySelector("#yue").innerHTML = mounth;

// 总天数
var days = 0;

// 总天数
var days = 0;
// 判断这一年是不是闰年
function runNian(y){
	if(y % 400 === 0 || (y % 4 === 0 && y % 100 !== 0)){
		return true;
	}else{
		return false;
	}
}

// 计算1980年到现在的头一年有多少天
for(var i = 1980; i < year; i++){
	if(runNian(i)){
		days += 366;
	}else{
		days += 365;
	}
 }

// 今年的1月打这个月的上一个月有多少天
for (var k = 1; k < mounth; k++){
	switch(k) {
		case 1:
			days += 31;
			break;
		case 2:
			if(runNian(year)){
				days += 29;
			}else{
				days += 28;
			}
			break;
		case 3:
			days += 31;
			break;
		case 4:
			days += 30;
			break;
		case 5:
			days += 31;
			break;
		case 6:
			days += 30;
			break;
		case 7:
			days += 31;
			break;
		case 8:
			days += 31;
			break;
		case 9:
			days += 30;
			break;
		case 10:
			days += 31;
			break;
		case 11:
			days += 30;
			break;
		case 12:
			days += 31;
			break;
	}
}

// 计算本月一共有多少天

var day = 0;
switch (mounth){
	case 1:
		day += 31;
		break;
	case 2:
		if(runNian(year)){
			day += 29;
		}else{
			day += 28;
		}
		break;
	case 3:
			day += 31;
			break;
		case 4:
			day += 30;
			break;
		case 5:
			day += 31;
			break;
		case 6:
			day += 30;
			break;
		case 7:
			day += 31;
			break;
		case 8:
			day += 31;
			break;
		case 9:
			day += 30;
			break;
		case 10:
			day += 31;
			break;
		case 11:
			day += 30;
			break;
		case 12:
			day += 31;
			break;
}

console.log(day);

// 计算上个月一共有多少天

var prevDay = 0;
switch(mounth - 1){
	case 1:;
		prevDay += 31;
		break;
	case 2:
		if(runNian(year)){
			prevDay += 29;
		}else{
			prevDay += 28;
		}
	case 3:
		prevDay += 31;
		break;
	case 4:
		prevDay += 30;
		break;
	case 5:
		prevDay += 31;
		break;
	case 6:
		prevDay += 30;
		break;
	case 7:
		prevDay += 31;
		break;
	case 8:
		prevDay += 31;
		break;
	case 9:
		prevDay += 30;
		break;
	case 10:
		prevDay += 31;
		break;
	case 11:
		prevDay += 30;
		break;
	case 12:
		prevDay += 31;
		break;
}

console.log(prevDay);

days += 2;
console.log(days);

// 计算出本月1号是星期几
var start = days % 7;
console.log(start);

// 计算一下当前页面的日历一共可以放多少天
var num = 42;

// 下一个月有多少天
var nextDays = num - start -day;

// 取到今天是几号
var thisdate = new Date().getDate();
var date1 = document.querySelector("#date1");
for(var j = prevDay - start + 1;j <= prevDay; j++){
	date1.innerHTML += "<span class='h'>" + j + "</span>";
} 
for(var a = 1; a <= day; a++){
	if(a == thisdate){
		date1.innerHTML += "<span class='today'>" + a + "</span>";
	}else{
		date1.innerHTML += "<span>" + a + "</span>";
	}
}

for(var s = 1; s <= nextDays;s++){
	date1.innerHTML += "<span class='h'>" + s + "</span>";
}




